diff --git a/OpenRA.Game/Traits/TraitsInterfaces.cs b/OpenRA.Game/Traits/TraitsInterfaces.cs
index 3f7d5e079e..73b9de1e94 100755
--- a/OpenRA.Game/Traits/TraitsInterfaces.cs
+++ b/OpenRA.Game/Traits/TraitsInterfaces.cs
@@ -81,11 +81,21 @@ namespace OpenRA.Traits
 	{
 		int2 PxPosition { get; }
 	}
+	
+	public enum SubCell
+	{
+		FullCell,
+		TopLeft,
+		TopRight,
+		Center,
+		BottomLeft,
+		BottomRight
+	}
 
 	public interface IOccupySpace : IHasLocation
 	{
 		int2 TopLeft { get; }
-		IEnumerable<int2> OccupiedCells();
+		IEnumerable<Pair<int2, SubCell>> OccupiedCells();
 	}
 	
 	public static class IOccupySpaceExts
@@ -96,10 +106,10 @@ namespace OpenRA.Traits
 			var nearestDistance = int.MaxValue;
 			foreach( var cell in ios.OccupiedCells() )
 			{
-				var dist = ( other - cell ).LengthSquared;
+				var dist = ( other - cell.First ).LengthSquared;
 				if( dist < nearestDistance )
 				{
-					nearest = cell;
+					nearest = cell.First;
 					nearestDistance = dist;
 				}
 			}
diff --git a/OpenRA.Game/Traits/World/Shroud.cs b/OpenRA.Game/Traits/World/Shroud.cs
index bd371a7bdd..8ef65361e5 100644
--- a/OpenRA.Game/Traits/World/Shroud.cs
+++ b/OpenRA.Game/Traits/World/Shroud.cs
@@ -136,7 +136,7 @@ namespace OpenRA.Traits
 			if (ios != null)
 			{
 				var cells = ios.OccupiedCells();
-				if (cells.Any()) return cells;
+				if (cells.Any()) return cells.Select(c => c.First);
 			}
 
 			return new[] { a.CenterLocation / Game.CellSize };
diff --git a/OpenRA.Game/Traits/World/UnitInfluence.cs b/OpenRA.Game/Traits/World/UnitInfluence.cs
index 9617c72901..9d7c776b69 100644
--- a/OpenRA.Game/Traits/World/UnitInfluence.cs
+++ b/OpenRA.Game/Traits/World/UnitInfluence.cs
@@ -26,9 +26,10 @@ namespace OpenRA.Traits
 		class InfluenceNode
 		{
 			public InfluenceNode next;
+			public SubCell subCell;
 			public Actor actor;
 		}
-
+	
 		InfluenceNode[,] influence;
 		Map map;
 
@@ -51,21 +52,32 @@ namespace OpenRA.Traits
 
 		public bool AnyUnitsAt(int2 a)
 		{
-			return /*map.IsInMap(a) && */influence[ a.X, a.Y ] != null;
+			return influence[ a.X, a.Y ] != null;
+		}
+		
+		public bool AnyUnitsAt(int2 a, SubCell sub)
+		{		
+			var node = influence[ a.X, a.Y ];
+			while (node != null)
+			{
+				if (node.subCell == sub) return true;
+				node = node.next;
+			}
+			return false;
 		}
 
 		public void Add( Actor self, IOccupySpace unit )
 		{
 			if (unit != null)
 				foreach( var c in unit.OccupiedCells() )
-					influence[ c.X, c.Y ] = new InfluenceNode { next = influence[ c.X, c.Y ], actor = self };
+					influence[ c.First.X, c.First.Y ] = new InfluenceNode { next = influence[ c.First.X, c.First.Y ], subCell = c.Second, actor = self };
 		}
 
 		public void Remove( Actor self, IOccupySpace unit )
 		{
 			if (unit != null)
 				foreach (var c in unit.OccupiedCells())
-					RemoveInner( ref influence[ c.X, c.Y ], self );
+					RemoveInner( ref influence[ c.First.X, c.First.Y ], self );
 		}
 
 		void RemoveInner( ref InfluenceNode influenceNode, Actor toRemove )
diff --git a/OpenRA.Mods.RA/Activities/CaptureBuilding.cs b/OpenRA.Mods.RA/Activities/CaptureBuilding.cs
index 27a6b0a7e0..ae719d5cbe 100644
--- a/OpenRA.Mods.RA/Activities/CaptureBuilding.cs
+++ b/OpenRA.Mods.RA/Activities/CaptureBuilding.cs
@@ -26,7 +26,7 @@ namespace OpenRA.Mods.RA.Activities
 			if (target == null || !target.IsInWorld || target.IsDead()) return NextActivity;
 			if (target.Owner == self.Owner) return NextActivity;
 			
-			if( !target.Trait<IOccupySpace>().OccupiedCells().Any( x => x == self.Location ) )
+			if( !target.Trait<IOccupySpace>().OccupiedCells().Any( x => x.First == self.Location ) )
 				return NextActivity;
 
 			// todo: clean this up
diff --git a/OpenRA.Mods.RA/Activities/Demolish.cs b/OpenRA.Mods.RA/Activities/Demolish.cs
index 616ec96eaf..506be2da10 100644
--- a/OpenRA.Mods.RA/Activities/Demolish.cs
+++ b/OpenRA.Mods.RA/Activities/Demolish.cs
@@ -26,7 +26,7 @@ namespace OpenRA.Mods.RA.Activities
 			if (IsCanceled) return NextActivity;
 			if (target == null || !target.IsInWorld || target.IsDead()) return NextActivity;
 			
-			if( !target.Trait<IOccupySpace>().OccupiedCells().Any( x => x == self.Location ) )
+			if( !target.Trait<IOccupySpace>().OccupiedCells().Any( x => x.First == self.Location ) )
 				return NextActivity;
 
 			self.World.AddFrameEndTask(w => w.Add(new DelayedAction(25 * 2,
diff --git a/OpenRA.Mods.RA/Activities/Infiltrate.cs b/OpenRA.Mods.RA/Activities/Infiltrate.cs
index 21b34ec97d..ddc4490526 100644
--- a/OpenRA.Mods.RA/Activities/Infiltrate.cs
+++ b/OpenRA.Mods.RA/Activities/Infiltrate.cs
@@ -25,7 +25,7 @@ namespace OpenRA.Mods.RA.Activities
 			if (target == null || !target.IsInWorld || target.IsDead()) return NextActivity;
 			if (target.Owner == self.Owner) return NextActivity;
 
-			if( !target.Trait<IOccupySpace>().OccupiedCells().Any( x => x == self.Location ) )
+			if( !target.Trait<IOccupySpace>().OccupiedCells().Any( x => x.First == self.Location ) )
 				return NextActivity;
 
 			foreach (var t in target.TraitsImplementing<IAcceptSpy>())
diff --git a/OpenRA.Mods.RA/Activities/MoveAdjacentTo.cs b/OpenRA.Mods.RA/Activities/MoveAdjacentTo.cs
index 4d6220f204..3cf7266aea 100755
--- a/OpenRA.Mods.RA/Activities/MoveAdjacentTo.cs
+++ b/OpenRA.Mods.RA/Activities/MoveAdjacentTo.cs
@@ -39,8 +39,8 @@ namespace OpenRA.Mods.RA.Activities
 			};
 			foreach( var cell in target.Trait<IOccupySpace>().OccupiedCells() )
 			{
-				ps1.AddInitialCell( cell );
-				if( ( mobile.toCell - cell ).LengthSquared <= 2 )
+				ps1.AddInitialCell( cell.First );
+				if( ( mobile.toCell - cell.First ).LengthSquared <= 2 )
 					return NextActivity;
 			}
 			ps1.heuristic = PathSearch.DefaultEstimator( mobile.toCell );
diff --git a/OpenRA.Mods.RA/Activities/RepairBuilding.cs b/OpenRA.Mods.RA/Activities/RepairBuilding.cs
index 0ce0c28286..b8f0a0f814 100644
--- a/OpenRA.Mods.RA/Activities/RepairBuilding.cs
+++ b/OpenRA.Mods.RA/Activities/RepairBuilding.cs
@@ -24,7 +24,7 @@ namespace OpenRA.Mods.RA.Activities
 		{
 			if (IsCanceled) return NextActivity;
 			if (target == null || !target.IsInWorld || target.IsDead()) return NextActivity;
-			if( !target.Trait<IOccupySpace>().OccupiedCells().Any( x => x == self.Location ) )
+			if( !target.Trait<IOccupySpace>().OccupiedCells().Any( x => x.First == self.Location ) )
 				return NextActivity;
 
 			var health = target.Trait<Health>();
diff --git a/OpenRA.Mods.RA/Air/Aircraft.cs b/OpenRA.Mods.RA/Air/Aircraft.cs
index fab016cd05..0178a72538 100755
--- a/OpenRA.Mods.RA/Air/Aircraft.cs
+++ b/OpenRA.Mods.RA/Air/Aircraft.cs
@@ -12,6 +12,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using OpenRA.Traits;
+using OpenRA.FileFormats;
 
 namespace OpenRA.Mods.RA.Air
 {
@@ -135,8 +136,8 @@ namespace OpenRA.Mods.RA.Air
 			}
 		}
 		
-		int2[] noCells = new int2[] { };
-		public IEnumerable<int2> OccupiedCells() { return noCells; }
+		Pair<int2, SubCell>[] noCells = new Pair<int2, SubCell>[] { };
+		public IEnumerable<Pair<int2, SubCell>> OccupiedCells() { return noCells; }
 
 		public void TickMove( int speed, int facing )
 		{
diff --git a/OpenRA.Mods.RA/AppearsOnRadar.cs b/OpenRA.Mods.RA/AppearsOnRadar.cs
index e64371f5d0..49d5f74394 100755
--- a/OpenRA.Mods.RA/AppearsOnRadar.cs
+++ b/OpenRA.Mods.RA/AppearsOnRadar.cs
@@ -36,7 +36,7 @@ namespace OpenRA.Mods.RA
 			{
 				if (Space == null)
 					Space = self.Trait<IOccupySpace>();
-				return Space.OccupiedCells();
+				return Space.OccupiedCells().Select(c => c.First);
 			}
 		}
 		
diff --git a/OpenRA.Mods.RA/Buildings/Building.cs b/OpenRA.Mods.RA/Buildings/Building.cs
index 9d8dd849e8..f0ee97001b 100755
--- a/OpenRA.Mods.RA/Buildings/Building.cs
+++ b/OpenRA.Mods.RA/Buildings/Building.cs
@@ -12,6 +12,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using OpenRA.Traits;
+using OpenRA.FileFormats;
 
 namespace OpenRA.Mods.RA.Buildings
 {
@@ -110,9 +111,9 @@ namespace OpenRA.Mods.RA.Buildings
 			get { return topLeft; }
 		}
 
-		public IEnumerable<int2> OccupiedCells()
+		public IEnumerable<Pair<int2, SubCell>> OccupiedCells()
 		{
-			return FootprintUtils.UnpathableTiles( self.Info.Name, Info, TopLeft );
+			return FootprintUtils.UnpathableTiles( self.Info.Name, Info, TopLeft ).Select(c => Pair.New(c, SubCell.FullCell));
 		}
 
 		public void OnCapture(Actor self, Actor captor, Player oldOwner, Player newOwner)
diff --git a/OpenRA.Mods.RA/Crate.cs b/OpenRA.Mods.RA/Crate.cs
index 2098e5d4cd..50fdf9b603 100644
--- a/OpenRA.Mods.RA/Crate.cs
+++ b/OpenRA.Mods.RA/Crate.cs
@@ -80,7 +80,7 @@ namespace OpenRA.Mods.RA
 		}
 
 		public int2 TopLeft { get { return Location; } }
-		public IEnumerable<int2> OccupiedCells() { return new int2[] { Location }; }
+		public IEnumerable<Pair<int2, SubCell>> OccupiedCells() { yield return Pair.New( Location, SubCell.FullCell); }
 
 		public int2 PxPosition { get; private set; }
 
diff --git a/OpenRA.Mods.RA/Husk.cs b/OpenRA.Mods.RA/Husk.cs
index b318ec7d00..a44d1acff1 100644
--- a/OpenRA.Mods.RA/Husk.cs
+++ b/OpenRA.Mods.RA/Husk.cs
@@ -10,6 +10,7 @@
 
 using System.Collections.Generic;
 using OpenRA.Traits;
+using OpenRA.FileFormats;
 
 namespace OpenRA.Mods.RA
 {
@@ -36,7 +37,7 @@ namespace OpenRA.Mods.RA
 
 		public int2 TopLeft { get { return location; } }
 
-		public IEnumerable<int2> OccupiedCells() { yield return TopLeft; }
+		public IEnumerable<Pair<int2, SubCell>> OccupiedCells() { yield return Pair.New(TopLeft, SubCell.FullCell); }
 		public int2 PxPosition { get { return Util.CenterOfCell( location ); } }
 	}
 }
diff --git a/OpenRA.Mods.RA/Mine.cs b/OpenRA.Mods.RA/Mine.cs
index 524f800422..8e0492bbe0 100644
--- a/OpenRA.Mods.RA/Mine.cs
+++ b/OpenRA.Mods.RA/Mine.cs
@@ -11,6 +11,7 @@
 using System.Collections.Generic;
 using OpenRA.Mods.RA.Activities;
 using OpenRA.Traits;
+using OpenRA.FileFormats;
 
 namespace OpenRA.Mods.RA
 {
@@ -53,7 +54,7 @@ namespace OpenRA.Mods.RA
 		
 		public int2 TopLeft { get { return location; } }
 
-		public IEnumerable<int2> OccupiedCells() { yield return TopLeft; }
+		public IEnumerable<Pair<int2, SubCell>> OccupiedCells() { yield return Pair.New(TopLeft, SubCell.FullCell); }
 		public int2 PxPosition { get { return Util.CenterOfCell( location ); } }
 	}
 
diff --git a/OpenRA.Mods.RA/Move/Mobile.cs b/OpenRA.Mods.RA/Move/Mobile.cs
index 2dd0c2d35f..4b8fd4df4e 100755
--- a/OpenRA.Mods.RA/Move/Mobile.cs
+++ b/OpenRA.Mods.RA/Move/Mobile.cs
@@ -271,13 +271,17 @@ namespace OpenRA.Mods.RA.Move
 
         public int2 TopLeft { get { return toCell; } }
 
-        public IEnumerable<int2> OccupiedCells()
+        public IEnumerable<Pair<int2, SubCell>> OccupiedCells()
         {
-            return (fromCell == toCell)
-                ? new[] { fromCell }
-                : CanEnterCell(toCell)
-                    ? new[] { toCell }
-                    : new[] { fromCell, toCell };
+            if (fromCell == toCell)
+				yield return Pair.New(fromCell, SubCell.FullCell);
+			else if (CanEnterCell(toCell))
+				yield return Pair.New(toCell, SubCell.FullCell);
+			else
+			{
+				yield return Pair.New(fromCell, SubCell.FullCell);
+				yield return Pair.New(toCell, SubCell.FullCell);
+			}
         }
 
         public bool CanEnterCell(int2 p)
diff --git a/OpenRA.Mods.RA/TargetableBuilding.cs b/OpenRA.Mods.RA/TargetableBuilding.cs
index e27801bd8d..76ca9d6390 100755
--- a/OpenRA.Mods.RA/TargetableBuilding.cs
+++ b/OpenRA.Mods.RA/TargetableBuilding.cs
@@ -11,6 +11,7 @@
 using System.Collections.Generic;
 using OpenRA.Mods.RA.Buildings;
 using OpenRA.Traits;
+using System.Linq;
 
 namespace OpenRA.Mods.RA
 {
@@ -32,7 +33,7 @@ namespace OpenRA.Mods.RA
 		public bool TargetableBy(Actor self, Actor byActor) { return true; }
 		public IEnumerable<int2> TargetableCells( Actor self )
 		{
-			return self.Trait<Building>().OccupiedCells();
+			return self.Trait<Building>().OccupiedCells().Select(c => c.First);
 		}
 	}
 }